New Orleans , Louisiana -LRB- CNN -RRB- -- BP said Sunday that it is `` pleased '' with how the operation to place a new cap on its ruptured undersea well is proceeding .

Officials hope the containment cap will stop oil from gushing into the Gulf . But while robots replace the old cap , crude is flowing freely .

The procedure -- expected to take four to seven days -- continued to progress Sunday as crews worked to position a transition spool over the gushing well to prepare for the new connection , according to BP 's Senior Vice President Kent Wells .

`` We 're pleased with how it 's going , '' Wells said , but cautioned that the operation , which began Saturday with the removal of the old cap , is only in its second day .

Robots removed six giant bolts from the apparatus early Sunday so that the new cap could be positioned .

If successful , the effects of the containment cap operation could halt the oil gusher that started April 20 after a deadly explosion on the Deepwater Horizon rig in the Gulf of Mexico .

But officials have said the new containment cap would be a temporary fix , and the permanent solution would still be completion of a relief well . There are two relief wells under construction .

Wells said Sunday that one of the relief wells could intercept the ruptured well as early as the end of July .

`` We 're feeling very good about how we 've positioned that well , '' he said .

The other relief well is expected to be completed in August .

The old cap had been diverting about 15,000 barrels a day -LRB- 630,000 gallons -RRB- to a ship . BP still is recovering an additional 8,000 to 9,000 barrels a day -LRB- 336,000 to 378,000 gallons -RRB- through a line connected to another vessel , the Q4000 .

`` As we start to ramp up the additional containment capacity , we should see less and less flow , '' Wells said .

The Helix Producer recovery vessel is expected to begin collecting oil Sunday evening , Wells said , and officials hope to reach its full collection capacity of 20,000 to 25,000 barrels -LRB- 840,000 to 1.5 million gallons -RRB- per day within three days .

Over the next two to three weeks , 60,000 to 80,000 barrels -LRB- 2.52 million to 3.36 million gallons -RRB- a day should be collected as part of the containment process , Wells said . Scientists estimate that 35,000 to 60,000 barrels of oil are spewing daily from BP 's breached well .

BP says there will be a period of decreased oil and gas capture from the wellhead during the cap replacement . It said another recovery vessel , the Q4000 , `` should continue to capture and flare oil and gas . '' There will be other recovery vessels and skimmers deployed .

Two more oil skimmers were added to the Gulf Sunday bringing the total to 48 collecting an oil and water mix from the surface , BP officials said . And another 15 burns were conducted in calm seas .

`` It was a good day in trying to contain the oil that made it out to the surface , '' Wells said .

Wells also said there will be `` significant measurement capability '' added to the new cap so officials can get a good idea of the flow rate .

BP said in a statement that the new cap `` should improve containment efficiency during hurricane season by allowing shorter disconnect and reconnect times . ''

Retired Coast Guard Adm. Thad Allen said Friday that the new cap would allow responders to collect more accurate oil flow data and that , once the switch is complete , the resulting capacity to contain oil `` will be far greater than the capabilities we have achieved using current systems . ''

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NEW : Crews position transition spool to prepare for new connection

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NEW : New recovery vessel expected to begin siphoning oil Sunday evening

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BP : Cap replacement is proceeding as planned

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Old containment cap removed from Gulf well

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Switch will take another 3 to 6 days , during which oil will flow unimpeded